1. Field of the Invention
The present invention relates to a linear light emitting diode (LED) module including a linear reflector and a linear LED bar and a backlight unit including the linear LED module without the need for a light guide plate.
2. Description of the Related Art
Backlight units are used in a wide range of applications, for example, LED TVs. Backlight units are broadly classified into edge-type backlight units and direct-type backlight units depending on the arrangement of light sources. In edge-type backlight units, a light guide plate (LGP) is arranged in rear of a display panel and LEDs are arranged at one lateral side of the light guide plate.
Conventional direct-type backlight units use a number of LEDs, whereas edge-type backlight units are advantageous in that the number of LEDs can be remarkably reduced. Nevertheless, direct-type backlight units have again attracted increasing attention due to high brightness of LEDs, low price of LEDs, and no need for expensive light guide plates. Direct-type backlight units are currently being developed that use a reduced number of LEDs to achieve a good distribution of light compared to conventional direct-type backlight units.
Direct-type backlight units are required to have a sufficient height because a sufficient distance between a display panel and light sources should be ensured. A lens may be used to widen a viewing angle of each LED, which is contrary to consumers' preferences for thin display devices, such as slim TVs. For these reasons, demand for edge-type backlight units is expected to rise steadily in the future.
Under these circumstances, there exists a need in the art for backlight units that can avoid the use of expensive light guide plates while maintaining advantages of edge-type backlight units that can contribute to a considerable reduction in a thickness of display devices. In order to meet this need, it is necessary to develop a technique by which light emitted from LEDs arranged at a rear edge of a display panel rather than in an area under a display panel is delivered to a reflective sheet positioned in rear of the display panel without the need to use a light guide plate. To this end, a reflector is used that serves to widely deliver light emitted from LEDs over the entire area of the reflective sheet.
In this technique, the reflective sheet may be provided with a slope or a gradient such that light delivered from the reflector is more uniformly reflected forward. The reflective sheet may be arranged such that its height is relatively small in areas adjacent to the LEDs and the reflector and gradually increases with an increasing distance from the LEDs and the reflector. The reflector is required to evenly deliver light emitted from the LEDs from the neighboring area to the distant area. However, a considerable portion of light emitted from the LEDs is not reflected from the reflector and reaches an edge area of the reflective sheet. That is, the reflector fails to evenly distribute light in the existing technology.
Other problems are that a printed circuit board (PCB) is difficult to bond to the reflector and the stability and reliability of the bonding are not sufficient. Further, overlapping of light emitted from the neighboring LEDs in LED arrays may cause non-uniform distribution of light. In the case where the distances between the LEDs increase to solve one or more of the problems caused by overlapping of light emitted from the neighboring LEDs, areas lacking supply of light are intermittently found over an entire surface of the display panel, making the problem of non-uniform light distribution more serious. Another problem exists in that non-uniform light distribution is caused by relatively bright areas around the edges of the display panel.